FUMARATE REDUCTION AND ITS ROLE IN THE DIVERSION OF GLUCOSE FERMENTATION BY STREPTOCOCCUS FAECALIS.

Deibel, R. H. (American Meat Institute Foundation, Chicago, Ill.), and M. J. Kvetkas. Fumarate reduction and its role in the diversion of glucose fermentation by Streptococcus faecalis. J. Bacteriol. 88:858-864. 1964.-Fumarate diverts the normal fermentation of glucose by Streptococcus faecalis FB82, as shown by the production of increased amounts of CO(2), formate, acetate, and acetoin, and decreased formation of lactate and ethanol. Experiments with d-glucose-1-C(14), in which low levels of labeled CO(2) were recovered, indicated that C-1 cleavage of the glucose molecule was not involved. The presence of fumarate afforded consistently larger cell crops in growth studies with glucose and other energy sources. On a molar growth-yield basis, anaerobically grown, glucose-fumarate cultures were equivalent to aerobically grown, glucose cultures. The reduction of fumarate by cell suspensions indicated that glucose, gluconate, and, to a lesser extent, glycerol and mannitol could serve as hydrogen donors. Several common metabolic inhibitors had no effect upon the fumarate reductase system in cell suspensions, although some sensitivity to acidic pH was noted. Significant levels of succinate oxidation activity were not detected. Fumarate reductase activity was demonstrated in all five S. faecalis strains tested. Distribution of this ability in S. faecium strains was variable, ranging from activity comparable with that of S. faecalis to total inactivity. The observations support the conclusion that fumarate functions as an alternate hydrogen acceptor, thus allowing pyruvate to participate in the energy-yielding phosphoroclastic and dismutation pathways.